On the XRP Ledger, an issuing account can be locked down so no one can mint more of a token. People call this 'blackholing'. It is not a flag you can point at; it is a conclusion you reach after checking every way an account could sign a transaction.

The control paths

First, the master key. If the account's lsfDisableMaster flag is set, the master key can no longer sign. Second, the regular key. An account can delegate signing to a RegularKey; that only counts as closed if the key is an address with no usable secret. Third, the signer list. An active SignerList object means a group of signers can still act. Fourth, any other known signing path.

How to check

Call account_info on the issuer against the validated ledger and read Flags and RegularKey. Then call account_objects with type signer_list. If every path is closed, the account has no known signing path left.

What this site does

The Ledger hub runs exactly those checks on every request and shows each control path individually, with the raw flag value and the validated ledger index it was read from. If one path is open, it says so rather than rounding up to a comfortable word.